Switchboard plug



1953 J J. ZIEMIANIN, JR 2,657,369

SWITCHBOARD PLUG Filed Dec. 6, 1951 2 Sheets-Sheet 1 INVENTOR. 76/322 JZzezwiazzirz .72:

M and M firlzeys Patented Oct. 27, 1953 UNITED STATES PATENT OFFICE 2,657,369 I swrrcn somn PLUG John J. Ziemianin, Jr., Chicago, Application December 6, 1951, Serial No. 260,122

This invention relates to'termi'nal plugs com prising electrical conductors; and'more' particularly to"a terrninalplug' for use in a telephone switchboard or the'like'.

Terminal plugs of'the type adapted for use in telephone switch boards generally comprise a' conductor plugadapte'dto be inserted in a'jack' holder which m'ounts'plural terminal contacts electrically connectedjto'a plural conductor cord. Such conductor plugsare' generally of a reversible type-in that theopposit'e'end portions thereof are electrically identical and" symmetrically configured. In the past, the various electrical conductingelements comprising the conductor plug have been separatelyiniilled' prior to assemblage, and the same is true forthe various insulators used to separate thecon'ducting' elements at the oppositeendportionsth'ereof. It is therefore an. object of the present inventionto eliminate such prior proceduresby means'of 'a novel blank which can be-machinedto a-finished conductor'plug in one operation and' 'wh'ich'can'be provided with internal insulation by" means of "injection molding.

Itis desirablethat'the conductor plug be reversib1e-in the jack holder without need for knockdown or'disassemblage of theparts" comprising-the jackholderjand it is therefore an object of the present'invention to afford means whereby this may be accomplished. Moreover, in this connection, it isdesirable that the plural terminal contacts be positioned on or in the jack holder by meansother than fixed metallic retaining; elements, audit is therefore an object of the present invention to confine rather than fix the terminal contacts relative to' the jack'holder.

Other objects of the'present invention will be apparent from thefollowing' description and the drawings," particularly with respect to the novel method ofmanufacturing"conductor plugs and.

themanner in which the terminal contacts are positioned in the jack holder.

In the drawings: V Fig.1 is a plan view of a'term'inal plugiembodying the features; of the'present invention; the outer shell beinggshown in section;

Fig; 2 isa sectional view taken substantially along the line 2 2 of Fig. 1 with certain parts shown-in elevation; I I I II Figs. 3,-4-and 5 are sectional'views taken substantially along the finest-3, 4 -4"and 5-5 of Fig 2; I I I I Fig; 6 is a sectional View similar toFig 2 but showing. the conductor plug in elevation and broken away; I I I I Fig. a sectional .viewa-snmlar to Figrfii Fig. 8 is a sectional view taken substantially along the line 88 in Fig. 6;

Fig. 9 is a horizontal sectional view taken through the jack holder;

Figs. wand 11 are-sectional views taken substantially alongthe lines Ill-l0 and Illl of Fig. 9;

Fig. 15 is a sectional view taken substantially along the line I5-l5 of Fig. 14.

In Figs. 1-14, the aspects of the present invention are illustratedas embodied in a terminal plug generally indicated at which comprises a conductor plug 20 either endportion of which is adapted to be releasably and reversably disposed in an inner housing or so-called jackholder 40, the latter carrying several spacedapart terminal contacts each provided with a contact spring which is adapted to engage a correspondingconducting section or element of the conductor plug". The conductor plug comprises terminal heads and collars paired with one another at the opposite ends thereof, such heads and collars being of electrically conducting material. An elongated sleeve, also of electrically conducting material, extends between opposite pairs of heads and collars, and the collars, sleeve, and heads are insulated one from an other. The jack holder 40 is generally cylindrical in shape and is formed on its periphery with elongated; spacedapart slots that permit radial movement of the contact springs relative to the jack holder during insertion and withdrawal of the'conductor plug.

Each of the terminal contacts is connected to a lead-in conductor of a plural conductor cord, and the terminal contacts are mounted on the jack holder in' such a manner as to be confined in position rather than fixed byscrews orinterconnecting conductors that ordinarily require tedious manipulations during assemblage and disassemblage.

Rerernng Figs. 1 and 2,-the conductor plug,

generally indicated at 20, is shown as being par. tially disposed in an-internal chamber 4! of a tubular jack holder 40. An outer tubular housing or shell fill'surrounds the jack holder and tends 'toconfine the terminal contacts as59 in a manner'to be described below. The outer housing"fillisopeniat'ioneend to permit insertion of -the"plug'20'into'theopn end of the jack holder,

and the other end 52 of the housing 60 is partially closed being provided with an opening for receiving one end of a triple conductor cord 6i. As best shown in Fig. 2, the conductor plug 253 is in the form of a substantially solid rod or cylinder the opposite end portions of which are symmetrically shaped and conductively identical so that the plug is adapted for reversal in the jack holder 40. The remote ends of plug 20 are provided with terminal heads 2! which are composed of electrical conducting material as for instance brass, and these heads 2| are insulated from enlarged diameter metallic collars 23 by means of hard rubber rings 22. The outer body portion of the plug 20 is in the form of an elongated conducting sleeve 28, the opposite ends of which are insulated from reduced diameter metallic collars 26 by other hard rubber rings 2's, and in turn these inner collars 26 are each similarly insulated from corresponding outer collars 23 by insulating rings 24.

Ordinarily, the various conducting and insulating elements of a plug such as 2e; are separately and accurately milled before being assembled. The present invention dispenses with such procedures and affords a novel blank and process by which the entire conductor plug can be machined in one operation, thus eleminating initial size tolerance considerations almost entirely. Moreover, since conductor plugs of this type embody internal insulators which must be molded or shaped separately within defined tolerances and then assembled manually, the present invention affords a method whereby the unfinished plug blank can be provided with internal insulation in a single step.

A blank 28A of the type embodied in the concept of the present invention is illustrated in Fig. 14 wherein the suffix A is used to designate unfinished or unmachined parts of the plug 28 previously considered in connection with Figs. 1 and 2. Thus, a central steel core 30 is formed with projections 3! of reduced diameter which are knurled as at 33. Concentric to but spaced radially from the steel core 38 is an internal steel sleeve 35 that is formed with a central opening 36 for a purpose to be described below. Concentric to but spaced radially from the steel sleeve 35 by bushing portions 25 on insulating rings 21A, is the outer bronze sleeve 28 previously considered. The ends of sleeve 35 project slightly beyond the insulating rings 21A so as to afford mounts for inner conducting collars 28A, the latter being insulated from outer metallic collars 23A by rubber rings 2 3A. It will be observed that the central bores in the collars 26A, 23A and the insulating ring 24A are of a diameter larger than that of the central core 30. A pair of brass bosses 2lA are pressed over the knurls 33 on the projections 3| and are separated from the outer metallic collars 23A by insulating rings 22A.

The plug blank 26A is most easily assembled by first slipping one of the rings 21A over one end of the inner conducting sleeve 35, after which the outer conducting sleeve 23 is positioned on the bushing portion 25 of the thus-assembled ring 21A. The other insulating ring TIA is then forced over the other end of sleeve 35 and into firm engagement with the other end of sleeve 28. The inner collars 25A are mounted on the projecting ends of sleeve 35, and then the rubber rings 24A, outer collars 23A, and rubber insulating rings 22A are arranged about the projections SI of the core 30. Finally, the bosses 21A are pressed over the knurls 33, and the outer collars and insulating rings which are loose on projection 3| are forced toward the inner collars 26A to limit positions. After the blank 26A is finally assembled in this manner, the internal structure thereof comprises a pair of spaced-apart annular channels st and 38 which separate, respectively, the facing sides of the sleeves and 28 and the facing sides of the core 38 and inner sleeve 35. The ends of the radial outer channel 33 are closed by the bushing portions 25 of the insulating rings 27A, while the radial inner channel 38 extends between and interconnects the conducting bosses ZIA.

Formed centrally on the outer sleeve 28 is annular boss that is tapped with a threaded aperture 5i; and an opening 29, the latter which is adapted to register with the opening 35 in the radial inner sleeve 35. Thus, both of the channels 34 and 38 are communicable with the opening 29, and the volume of these channels can be filled with an insulating resin of a suitable free-lowing type by injecting the resin material, under pressure, through opening 29 and subsequently setting the same. It will be appreciated that the particular resin will be largely a matter of choice, the primary requirements being free-fiowability, optimum insulating characteristics, and ability to remain set within expected temperature conditions. As a result, the inner sleeve 35 is insulated from the core 3% as well as from the outer sleeve 28 by resin insulating sleeves 39, Fig. 2, the resin also flowing into the sections of channel 38 lying between the inner ends of the bosses ZIA and the ends of the sleeve 35. It will be seen that the bosses 23A are electrically interconnected through core 3t and the projections 3i thereof, and that the inner collars 26 are electrically interconnected through the inner sleeve 35. As shown in Fig. 14, the ends of the projections 31 extend beyond'the bosses 2 EA and are adapted to be held in a lathe whereat the electrically identical end portions of the plug blank 28A can be symmetrically machined to assume the finished configuration shown in Figs. 1 and 2. The annular channels 3 and 58 are preferably filled before machining since the resin will then tend to adhere to exposed parts, especially the rubber insulator rings, and prevent rotation thereof relative to core as during machining. However, I have found that when the terminal bosses 2 IA are pressed over the hnurls 33 and firmly forced toward one another to limit positions, the collars, insulating rings, and sleeves are frictionally locked to such an extent as to assure rotation of all parts with the core 30 and the projections 31 thereof during machining. Considered from the standpoint of the internal insulating method involved and the purpose thereof, it will be appreciated that the conductor plug blank as 26A may assume several structural modifications by way of design insofar as the insulator-filled channels and the insulator rings are concerned, the essential feature being that the conductor plug blank as presently conceived may be machined in one operation and the internal conductors thereof insulated by a single step.

The jack holder id is generally tubular in form and preferably composed of an insulating plastic. The recess ii, in which the plugit is to be partially disposed, terminates at the forward end of a. body portion as of holder it. The rearward end of the body portion M is formed with a central I recess 35 wherein one end of the triple conductor cord ti terminates. A fiber shell or outer tube tilencases the jack holder, and the open end of this housing projects beyond the forward open end-of thejack holder so as to provide an inter.- nal shoulder against which the boss 55 on the plug 26 is adapted toabut when thelatter is fully and properly inserted in the jack holder. At its for- .ward end, the housing 60 is formed with an opening which isadapted to register with the threaded aperture 56 in the boss 55 so thata set screw 51, Fig. 1,-can be used to lock plug 20 against displacement from the, jack holder.

When plug 2-0 is inserted in the jack holder, the conducting elements 2|, 26 :and 23 thereof are each engaged by one of three terminal contacts 56, 1-0 and8|l of a type generally indicated as 50, Fig. 13. These terminal contacts as-55 are mounted in position on the body portion '44 of jack holder *40 and are spaced .120" apart from each other as .best shown in Fig. v8. fiorresponding substantially to the. spacing between the aforesaid terminal contacts, three elongated slots -42 are spaced 120 from each other about the periphery of the jack holder 40. As best shown in Figs. 1 and 12, the-slots 42 terminate short of the :forward end-of the jack holder and open at the rearward end thereof so that portions of th'eserslots 'are coextensive :in length with the recess 45 at the rear of the jaok' holder 6H. Formed intermediate the ends of each of the slots-42 are a .pair of transverse slots 43 .thatextend into the :body portion 44 .of the jack .holder, and it is these latter slots which function in part to maintain the terminal contacts as 56 in position on the jack holder.

While the three longitudinal slots 42 are conveniently of the same length, the terminal contacts mounted on the jack holder are formed with contact elements or springs each of different lengths. Thus, there :is .a terminal contact 55, Fig. 2, provided with a short acontact spring v352 that is adapted to engage a conducting head 2| of .the plug 25; a terminal contact l0, Fig. '7, provided with .a contact spring 120ian intermediate length adapted to engage a conducting collar 28 of the conductor plug; and a terminal contact-.35, '6, provided with a long contact spring 32 adapted to engage a conducting sleeve 2310f plug :25. Each terminal contact is generally of the same configuration and, as best shown in Fig. 13, comprises a sleeve element as 5| and a pair of transverse arms as 53 which project-from the contactspringasfl. The body portion 44 of thejack holder-4E is formed with recesses 41, 43,23 116! 49; spaced. 120? apart so as to afford housings for the sleeves 5|, H and 8| of each of the three terminal contacts. When positioned on the jack holder, these sleeve elements 5|, H and 8| rest in the corresponding housings 47, 48 and 49, and the pairs of transverse slots 43 receive the transverse arms 53, 13 and 83. The transverse arms hold the terminal contacts against horizontal displacement, and as shown in Fig. 8 vertical displacement from the jack holder is prevented by engagement between the inner sides of shell 60 and the sleeve elements 5|, 1| and 8| of the terminal contacts. One end of the cord 5| is disposed in the rearwardly opening recess 45 of the jack holder 40, and lead-in conductors 54, 14 and 84 are clamped in the corresponding sleeves 5|, H and 8| of the terminal contacts. It will be appreciated that the contact springs as 52 normally bear firmly against the corresponding conducting elements of conductor plug 20 and, when the latter is removed from the jack holder. spring part way into the longitudinal recess 4|, that is to say, are inclined radially inwardly of the slots 42 when the plug 20 is removed -Vf-rom the jack h lder- (In sequently, when current is present in the con ductor cord 6i and therefor in the lead-in wires, .ooth conducting heads 2| are charged through the interconnecting metallic core 30 and ;both conducting collars 26 through the interconnecting metallic sleeve 35.

From the above, it will be seen that the plug 253 can be reversed simply by loosening the set screw 51 and withdrawing the plug 20 from out of the jack holder :40, the :novel arrangementbetween the terminal contacts and the slotted jack holder permitting reversal of the conductor plug without need for further knockdown ordisas-e semblage. In the event that one of the contact springs becomes worn or loses itsresiliency, or the effectiveness of the terminal contact othe wise becomes impaired, the latter can be replaced simply by removing the outer shell 50, disconnecting the appropriate ,lead-in eondpctor, and dropping a new terminal ;contact,-into position on the body portion 44 of the jack holder. It will be seen that the terminal .09 tacts are confined rather than fastened in position, and moreover, .being spaced apart from each other, do not require insulation to prevent short circuiting.

While the aspects of thepresent invention hare been described from the standpoint ofa three conductor terminal plug, :it will be appreciated that corresponding chan es :for other types .can be made as required without departing from the concepts and scope of practice set forth. The specific composition for the .variousgconducting elements and insulators of the conductor plug is largely a matter of choice, thepreferred types being described by way :of illustrationjrather than exclusion or limitation. The appended claims are statement of what I presently consider to be the characterizingfeatures and manifestations which embody the .novel concepts of the present invention, distinguishing the .same ;-irom others in the art.

I claim:

1. In a terminal plug for use telephone switchboards or the like, a conductor plug having symmetrical end portions whereby the conductor plug is reversible in a holder, a cylindrical holder formed with spaced apart slots on its periphery and having an elongated central recess therein for receiving the conductor plug, the elongated recess terminating at a body portion of the holder, other slots extending transversely of each of the first-named slots and extending into the body portion of the holder, terminal contacts mounted on the body portion of the holder and each having a contact spring with arms extending transversely therefrom, the terminal contacts being spaced apart from each other with the arms thereof positioned in the said other slots and the contact springs thereof freely disposed in the first-named slots, the contact springs being adapted to engage difierent conducting elements of the conductor plug, and an outer shell surrounding the holder whereby the terminal 7 contacts are maintained in position about the body portion of the holder.

2. In the terminal plug according to claim 1, a boss located centrally on the conductor plug, the outer shell projecting beyond the corresponding end of the holder to thereby define an itntfirnal shoulder against which the boss is abut- 3. In a terminal plug for use in telephone switchboards or the like, a conductor plug having symmetrical end portions whereby the conductor is reversible in a holder, a tubular holder for the conductor plug having a longitudinal recess terminating at a rearward body portion in the holder, the periphery of the holder being formed with elongated spaced-apart slots and other slots extending transversely of each of the elongated slots, the said other slots also extending into the body portion of the holder, terminal contacts mounted on the body portion of the holder and each comprising a spring contact with arms extending transversely therefrom, the terminal contacts being spaced apart from each other with the spring contacts each positioned in the corresponding elongated slots and the transverse arms being disposed in the corresponding said other slots, the contact springs being adapted to engage difierent conducting elements of the conductor plug, and an outer shell surrounding the holder whereby the terminal contacts are maintained in position about the body holder.

4. In the terminal plug according to claim 3, a boss located centrally on the conductor plug, the outer shell projecting beyond the corresponding end of the holder to thereby define a shoulder against which the boss is abuttable.

5. A holder of the type adapted to slidably receive a switchboard plug comprising, an elongated tube-like member recessed axially to receive one end of said plug, said. recess terminating short of the rear of said plug to thereby afford a body portion in the holder, a longitudinal slot formed in the periphery of said tube-like member to correspond to a conductor element of said plug, a pair of transverse slots at the rear of said longitudinal slot with one such transverse slo-t being formed at either side of the longitudinal slot, said transverse slots each extending down into said body portion, and a terminal contact mounted in said holder, said contact having an elongated spring contact element disposed in said longitudinal slot whereby the spring contact may move radially out and in without respect thereto, and a pair of transverse arms respectively extending at right angles from respective sides of said spring contact, said transverse arms being seated in said transverse slots whereby said terminal contact is anchored to said holder.

6. A holder according to claim 5 comprising an outer tube removably mounted in concentric relation to said tube-like member with a. portion of the underside of said outer tube engaging the top side of said terminal contact toprevent displacement of the latter relative to said holder.

7. A holder of the type adapted to slidably receive a switchboard plug comprising, an elongated tube-like member recessed axially to receive one end of said plug, said recess terminating short of the rear of said plug to thereby afiord a body portion in the holder, a plurality of longitudinal slots formed in the periphery of said tube-like member in spaced relation one to another, each of said slots corresponding to a different conductor element of said plug, each of said slots being provided with a set of transverse slots which extend down into said body portion whereby there are spaced apart sets of transverse recesses in said body portion, and a plurality of terminal contacts mounted on said body portion in said spaced relationship whereby there is afforded a terminal contact for each conducting element of the plug, each of said terminal contacts having a spring contact element disposed in a corresponding one of the longitudinal slots for movement toward and away from said recess, and each of said terminal contacts having a set of relatively short transverse arms extending from either side of the respective spring contact elements and seated in respective sets of said transverse slots whereby the terminal contacts are anchored to said body portion.

8. A holder according to claim 7 comprising an outer shell concentrically and removably mounted on said tube-like member, the underside of said outer shell engaging the top sides of said terminal contacts and thereby serving to prevent displacement of said terminal contacts relative to said holder.

JOHN J. ZI'EMIANIN, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,302,471 Richter Apr. 29, 1919 1,837,723 McGraw Dec. 22, 1931 FOREIGN PATENTS Number Country Date 508,006 Germany Sept. 11, 1930 

